With the development of the communication technology, the communication of the mobile terminals such as a cellphone has entered in the third Generation (“3G” for short), wherein the video call in the multimedia applications, as an upgrading of the voice call, has become one of the most important services and applications of the cellphone.
At present, the multimedia applications and other data services have quite high demands to the channel capacity of communication. Some users can not use the video call service or the users that are using the video call service are caused to be disconnected when the channel capacity of the cell does not satisfy the video call service of all video terminals belonging to the cell.
Therefore, how to guarantee the users to use the video call service to a maximum extent and to transform it into a common voice call without interruption when the video call service can not be used greatly influence the quality of the 3G service and the user experience, which is also a research emphasis in the initial stage of 3G.
However, effective solutions have yet not been provided to the problems that a self-adaptive adjustment can not be carried out between the video call quality and the channel capacity, thereby affecting the service quality of the whole user group, and how a reasonable transformation is made between the video call and the voice call